A six week placebo controlled trial of the efficacy and saftey of 6 g of 4-Aminosalicylic acid (4-ASA) was conducted in 30 subjects with mild to moderately severe ulcerative colitis. Subjects were stratified into groups having distal (<60 cm) or more extensive (>60 cm) disease. Diarrhea, bleeding, sigmoidoscopic and biopsy appearance and physician global assessment were scored to judge efficacy, and safety was evaluated by monitoring untoward symptoms and laboratory values. Median percent improvement was significantly greater (p<.05) in the 4-ASA > 60 cm group (42.7) than in the placebo > 60 cm group (21.2), but 4-ASA was not better than placebo for the <60 cm group or the total study group. Severe dyspepsia (1) and abnormal AST (1) and lipase without pancreatitis (1) occurred. Thus 6 g 4-ASA for six weeks was more effective than placebo in mild to moderate ulcerative colitis >60 cm above the anus, but not in distal disease. The statistical analysis of the data collected on subjects seen in previous years was completed using the CDMAS resource.